Wall flow reactor for hydrogen production

Abstract

Disclosed herein are wall flow reactors that are suitable for the production of hydrogen gas from hydrocarbon and / or its derivative feed streams. The wall flow reactors are generally comprised a monolithic honeycomb substrate defining a plurality of cell channels bounded by porous channel walls that extend longitudinally from an upstream inlet end to a downstream outlet end; wherein a first portion of the plurality of cell channels are plugged at the downstream outlet end to form inlet cell channels and a second portion of the plurality of cell channels are plugged at the upstream inlet end to form outlet cell channels. A plurality of catalyst layers are positioned within at least a portion of the plurality of cell channels and comprise at least a first catalyst layer and a second catalyst layer. Also disclosed are methods for treating reactant feed streams.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a process and apparatus for the production of hydrogen gas from a hydrocarbon and / or its derivative feed streams.[0003]2. Technical Background[0004]Much interest has recently been directed to hydrogen gas (H2) as U.S. Administration's future fuel of choice. In particular, hydrogen fuel is now required for use in many energy related processes. For example, hydrogen fuel cells represent an exemplary energy related application that has received increased attention in recent years as a possible substitute for energy dependency on gasoline and related non-renewable fossil fuels. To this end, hydrogen can for example be produced by cracking natural gas. However, the expense associated with this process is typically up to four times more expensive than the cost of gasoline. Therefore, to make H2 a more widely available commodity, it is necessary to develop more efficient high-throughput H2 prod...

AI Technical Summary

Benefits of technology

[0011]The present invention provides a wall flow reactor which enables the staging of multiple thin catalyst layers in a manner that at least substantially eliminates the problems associated with conventional devices and processes described above. For example, by staging the multiple thin washcoat layers on a porous monolithic honeycomb substrate walls, it is possible to internally couple exothermic and endothermic reaction in such a way that the exothermic methane oxidation occurs on the one catalyst layer with CO, CO2 and H2O produced as main products. Those products, together with excess methane passing to the second catalyst layer which has desired endothermic methane reforming function, can result in a relatively high ratio of H2 and CO production. If desired, these H2-rich product streams can further pass in contact with a Water-Gas-Shift catalyst layer to maximize even more H2 production and even lower the CO content. One can pursue this embodiment by sequentially staging multiple thin layer washcoat catalysts.

[0012]In one embodiment, the wall flow reactor of the present invention can provide a sequential staging of multiple washcoat catalyst layers in such a way that there is at least substantially no possibility of different catalyst mixing since the active catalytic components (e.g., precious metal) are fixed inside washcoat. Still further, the reactor can be scaled up in both diameter and reactor length without causing high pressure-drop and flow maldistribution since the pressure-drop is no longer dependent on the diameter and is at least less dependent on the length of the wall flow reactor of the present invention.

[0015]Among several advantages that can be exhibited by the devices and methods of the instant invention is reactant flow having a substantially uniform flow path through a washcoat substrate wall layers. Even at high superficial gas velocity (high-throughput), the pressure-drop of reactor is still lower comparing with those conventional granular and foam catalyst beds. Further, by controlling substrate channel wall thickness and the permeability of the channel walls, one can control or optimize flow residence time and the pressure-drop through the channel walls. In one embodiment, the permeability of the channel walls can be controlled or optimized by providing channel walls having desired pore microstructures. In still another embodiment, there is substantially no internal diffusion limit due to the thin washcoat catalyst layers. Additionally, the wall flow reactor can be scaled up without limitation to increase productivity per reactor. For example, the reactor can be scaled up by increasing the reactor diameter and / or the reactor length without changing the channel scale transport and reaction features.

Problems solved by technology

However, the expense associated with this process is typically up to four times more expensive than the cost of gasoline.

Coupling these endothermic and exothermic reactions is very difficult using conventional granular type catalyst fixed-beds as it is very difficult to maintain staged thin layers of catalysts position-fixed all time.

Similarly, use of the foam monoliths described above makes it very difficult to machine the bulk monolith into a very short monolith layer (few millimeters to few center meters), especially when the diameter of the monolith is relatively large Further, it is also challenging to make an active catalyst deposition on a “pan-cake” shaped foam monolith uniform.

With respect to catalyst and reactor scale up, it is also quite challenging to manufacture a relatively large diameter reactor (e.g., D˜1.0 m) with multiple layers of different catalysts (layer thickness˜few cm) and with very short reactor length.

In particular, one cannot simply increase the layer thickness because of the limitation of the total pressure-drop especially when the small granular catalysts are used.

Thus, to make the entry flow a uniform distribution is another challenge especially for such a large diameter pan-cake shaped reactor.

Still further, adding too many inert layers for better flow distribution often ends up with high pressure-drop increase.

Because of the limitation of big reactor diameter and limitation of using thick packing layers, one has to increase the number of “pan-cake” type reactors to meet certain productivity needs, which will increase both capital and operational costs of the process.

Images